Comparing lengths by measuring
Measure to determine how much longer one object is than another, expressing the length difference in terms of a standard length unit
What a learner can do afterwards
- Measure two objects and calculate the difference in length
- Express the difference using the correct unit (e.g. '7 cm longer')
- Solve a comparison problem: 'How much taller is the bookshelf than the desk?'
The lesson
You already know how to measure things with a ruler. Now you will compare two lengths. Measure each object in the same unit, like centimeters. Then subtract the smaller number from the bigger number. That number tells you how much longer one thing is.
Mia measures her book and her notebook. The book is 20 cm long. The notebook is 13 cm long. She subtracts: 20 minus 13 equals 7. The book is 7 cm longer than the notebook.
Always measure both objects with the same unit, like centimeters for both. Then your subtraction gives a fair answer, and remember to say the unit, like '7 cm longer'.
Measure both objects in the same unit, then subtract to find how much longer one is.
Watch it
Where it sits
Learn first
This opens up
Where this leads
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.